1. Field Of The Invention
This invention relates to a dental post construction for use in anchoring a tooth restoration to a portion of an injured tooth.
2. Description Of The Prior Art
When repairing severely damaged teeth, a dental post is often utilized to help anchor a tooth restoration such as an artificial crown to a remaining root portion of a tooth. For example, the crown may be broken from a tooth by a traumatic injury or may have substantial portions thereof removed due to removal of decayed areas, thus leaving the root or roots of the tooth along with a relatively short stub of the original crown extending above the patient's gum area.
When the damage to the tooth is such that it is necessary to remove the pulp material from the root canals, it is common to use an endodontic post to help anchor the artificial crown to the remaining original tooth structure. An endodontic post is a cylindrical pin which is cemented into the endodontically prepared root canal and extends above the surface of the remaining natural tooth to serve as an anchor for the artificial crown restoration which is attached to the remaining natural tooth.
In multi-canaled teeth such as molars, there will typically be two such posts, one placed in each of two separate canals. In single-canaled teeth, typically a single cylindrical post will be placed in the canal.
A general description of these prior art procedures utilizing endodontic posts, both in multi-canaled and single-canaled teeth is provided in "Preparing Severely Damaged Teeth", March, 1983, CDA Journal, pages 85-91 by Shillingburg, Jr., et al.
The posts utilized for such tooth restorations are typically cylindrical, often having grooves, threads or flutes formed in the post for aid in cementing the post in place and/or venting cement from the root canal as the post is placed in the canal.
Typical prior art posts are disclosed in the Shillingburg, Jr., et al. article, and also in U.S. Pat. No. 4,479,783 to Weissman.
The difficulty with these prior art post constructions arises primarily in teeth having a single-canaled root. There, the use of a single cylindrical post cemented in place in the canal is sometimes unsuccessful, because the substantial forces applied to the artificial crown during biting and chewing may apply rotational forces to the crown about the longitudinal axis of the post, often causing rotation of the post within the canal and resulting in the artificial crown breaking away from the natural portion of the tooth.
One prior art multi-post construction is shown in U.S. Pat. No. 758,750 to Haldeman. The Haldeman structure, however, utilizes two semi-cylindrical posts which when fitted together result in a post construction having a circular cross section which still is susceptible to rotation within the root canal.
The prior art also includes irregularly shaped single-piece dental posts which are contoured to fill an oval-shaped upper portion of a root canal. For example, in U.S. Pat No. 4,600,392 to Weissman, a dental post is provided having projecting ribs on either side. A special jig must be utilized to drill the tooth canal to an appropriate shape to receive the contoured dental post.
Another dental post construction similar to that of the Weissman '392 patent is shown in U.S. Pat. No. 4,708,655 also to Weissman.